There are many instances in which a relatively large mirror is needed in order to provide visibility to an operator who cannot be present at a location to observe something directly with his or her eyes. A very common situation in which this occurs is when the driver of a large vehicle needs to see what is happening alongside or behind the vehicle before backing or making a maneuver such as a turn. Hence, this invention will be described as if it were being used on a large vehicle like a truck, but it should be understood that the mirror assembly could also be advantageously used in other environments, including trains, boats, or even static devices. For example, the operator of a large machine may have a need to adjust the position of a mirror so that the intake or output of the machine can be personally monitored. If the machine is subject to the same kind of vibration that a large truck experiences, then the machine operator may need a mirror in much the same way that the driver of a truck does. So the mirror assembly disclosed herein should be recognized as having utility in essentially static situations as well as mobile ones.
Relatively large vehicles such as trucks, buses, large recreational vehicles and the like have requirements for external mirrors that are significantly different than those for automobiles and motorcycles. In the case of large trucks and the tractors that provide the motive power for multi-wheel rigs (e.g., 18-wheel rigs), there are rather extreme vibrations that attend a vehicle's travel along highways at speeds in the neighborhood of 55 miles per hour. To deal with such vibrations, there has developed what amounts to an industry standard for external mirrors, namely, that a large and generally rectangular mirror be supported at its top and its bottom by a bracket that is firmly anchored to the tuck or tractor. The bracket may be best described as being essentially C-shaped, with the opening of the "C" facing toward the vehicle. Such brackets are sometimes referred to as "West Coast" brackets. Near the distal ends of the C-shaped bracket, two apertures are provided at locations such that two spaced bolts (and complementary nuts) may be employed to secure a mirror assembly at its top and bottom. The two spaced and aligned bolts define a generally vertical axis that passes longitudinally through a rectangular mirror housing that is usually about 17 inches tall.
It has been common to provide for adjustment of such a truck mirror about its vertical axis--both to the right and to the left, because truck drivers come in all shapes and sizes, and their respective lines of sight to a mirror may vary significantly. For a mirror assembly that is located on the driver's side of a cab, it might be possible to simply reach out and grab the mirror and physically twist it against whatever restraining force is realized from the mounting bolts. But if it is raining or snowing, there's little pleasure in the chore of rolling down a window and reaching out to push or pull on one edge of a mirror. In the case of the mirror on the right (or passenger) side of a truck, there is no way that a driver could safely reach all the way across the cab to make an adjustment. Of course, in automobiles and in truck cabs that do not tilt, it might be possible to connect certain mirrors with flexible cables, so that a driver might twist a know that is connected to one end of a cable and rotate a mirror at the other end of the cable. But with large mirrors that are subject to wind loads and road vibration, the mirrors must usually be held so tightly by their mounting bolts that making an adjustment with a flexible cable becomes so difficult as to be of doubtful value. Furthermore, cable-operated systems are especially susceptible to becoming frozen when a truck is driven in icy or known conditions.
Even if a driver succeeds in obtaining a suitable adjustment of his or her outside mirrors before starting on a trip, the mirror-adjustment process is not necessarily over. For example, one situation that frequently occurs in urban areas is that a driver of a tractor/trailer rig wants to make a right turn; and often the driver feels compelled to wing out into the left lane in order to provide sufficient clearance for the trailer as the turn is executed. Without such wide turns in a congested area, the trailer might come into contact with a traffic light standard, a fireplug, a sign or a telephone pole. But even though most trailers carry warning signs to let motorists know of the risks of trying to pass a turning tractor/trailer rig on the right while it is turning right, there are still too many impatient automobile drivers who think they have just enough time to "squeeze by" before the tractor actually begins its turn. The result is sometimes a seven-foot automobile that's been crushed and squeezed sideways into a four-foot space between a trailer and a telephone pole.
While it is true that the driver of such an automobile must usually bear most of the blame for causing such accidents, it would be nice if the driver of the tractor could glance at what's alongside his or her trailer as the right turn is being executed. Of course, such visibility would be available only if the mirror could be temporarily swung outwardly, because tractor mirrors are conventionally adjusted to provide the driver with a view of what's at the rear of a trailer--not what is immediately alongside it. And after the turn has been completed, the tractor's mirror needs to be swung inwardly (about a vertical axis) so that the driver is again viewing what's at the trailer's rear.
To meet the above requirements, some mirrors have been rotated by small motors that are positioned immediately behind the reflective surface of a mirror. Examples of such "motorized'8 mirrors are disclosed in U.S. Pat. No. 3,132,201 to Bertell et al. entitled "Outboard Rear Vision Mirror For Trucks And The Like," U.S. Pat. No. 3,610,736 to Bateman entitled "Power-Driven Rear View Mirror," and U.S. Pat. No. 4,464,016 to Weber et al. entitled "Power-Adjusted Mirror With Motor On Housing And Offset Center Wheel." While the general concept of each of these prior art mirrors was perhaps good, there has been a major difference between what seems reasonable in theory and what works in the real world. In fact, just a few years ago a major manufacturer of mirrors for trucks, tractors and buses introduced a mirror assembly which it assumed would address all of the problems of inadequate visibility that were mentioned above. But no matter how commendable the goal, the new mirror was a total failure; and within two years there had been a 100 percent recall of all mirrors that had been shipped to customers. And this recall was not of minor proportions; it involved thousands of very expensive mirrors.
Perhaps one reason for the surprising 100 percent failure of the aforementioned mirror was the failure of the manufacturer to recognize that most truck drivers (and the companies that hire them) usually like to operate clean rigs. And not long ago many people in the trucking industry discovered that a mild acidic solution will clean the exterior of a truck and trailer much faster and more thoroughly than simply pressurized water. Therefore, many maintenance facilities and truck-washing stations began to add a small amount of acid to their wash water. For those electrical parts that were not protected against the presence of acid, even in a weak solution, the results were corrosion and rather quick failure. It will be seen, therefore, that there has remained a need for a dependable and practical apparatus for rotating an external mirror, to improve visibility behind and alongside a long vehicle. It is an object of this invention to satisfy such a need.
It is a further object to provide an exterior mirror for trucks and similar large vehicles that is not subject to failure from the cleaning liquids that can enter a mirror housing and eventually migrate to where they contaminate everything within the housing.
Still another object is to provide a rotatable mirror that can be mounted on the kind of vehicle that is known to experience severe vibration, but which can be mounted so tightly that the mirror can still give the driver a stable image when he or she wants to see what's happening at the rear of the vehicle.
One more object is to provide a rotatable mirror with a clutch that can protect a motor that is used to rotate the mirror--if the mirror comes into contact with an immovable object (such as the mirror mounting bracket).
These and other objects will be apparent from a reading of the specification that follows, together with the claims that are appended thereto--and the accompanying drawings.